Strike-slip faulting, topographic growth and block movements as deduced from drainage anomalies: The Yeşilırmak River basin, northern Turkey

- The Yeşilırmak River drainage basin divided into several faulted wedges by right-lateral strike-slip faulting of the North Anatolian fault zone and its individual splays.
- Geomorphic offsets are highest along the North Anatolian fault and decrease on the splay faults toward south consistent with the GPS data.
- Deflections represent a superimposed development, and probably a still ongoing topographic growth in the region.
- The Sungurlu-Ezinepazarı fault has a critical role in the landscape evolution of the drainage basin.
- The Black Sea level changes should modified the fluvial network during the Quaternary period, particularly in the late Quaternary.

This study aims to understand the various effects of known tectonism on a fluvial network and to interpret the tectonic deformations using described, and analysed systematic anomalies in the drainage basin of the Yeşilırmak River in northern Turkey at countermarch. This region, which is divided into several faulted wedges by right-lateral strike-slip faulting of the North Anatolian fault zone and its individual splays, has experienced several moderate to large earthquakes with high amounts of surface ruptures during the historical and instrumental periods. The Yeşilırmak River basin includes several geomorphic imprints of such widespread and frequent strike-slip deformations. Offsets (between 750 m and 19 km), aligned drainages, and linear valleys (170 km) are expected geomorphic and tectonic responses to strike-slip faulting in the fluvial system. We used such indicators to determine the long term effects of strike-slip faulting in the Yeşilırmak River drainage network. The measured stream offsets represent decreasing values toward southern splay faults consistent with published geodetic data for the region. However, some other large-scale geomorphic anomalies extracted from the drainage network are not explainable by only strike-slip tectonics. Compressional structures, i.e., anticlines, synclines, in the region are responsible for such large-scale drainage diversions (20-24 km) along the river courses. Although these diversions, the North Anatolian fault zone is the main driving force shaping present geomorphology on a regional scale. The Sungurlu-Ezinepazarı fault also plays a critical role in landscape evolution. Their activities and associated block movements have resulted with tilting processes. On the other hand, the entire fluvial network should be modified by the sea level changes of the Black Sea, particularly in the late Quaternary.